I have an ASUS M2N-MX SE motherboard with AMD Athlon X2 64 4000+ CPU

My Graphics Card chip type is NVIDIA GeForce 6150SE nForce 430

Now, of late I am having this weird problem, the problem is that in the middle of normal PC operations [such as browsing websites] my screen just scrambles up and the PC freezes.

The screen appears to be like this

Once this happens, the only solution for me is to reset my PC and on resuming it happens again.

I remember having this problem once about a year back, later I updated the display drivers from NVIDIA and it was running fine until today when this problem started again....and now it's much more frequent.

Kindly advise.